In the early 1980s, the typical exhaust gas heat exchangers were the so-called tube bundle heat exchangers, which consist of a bundle of round tubes that are connected at both ends to tube sheets to pass fluid therethrough. See, for example, German Utility Patent No. 83 19 866. The inlets and outlets for the exhaust gas are situated at opposite ends. Collection spaces are also formed there, from which the exhaust gas is distributed into the individual tubes of the bundle and flows through it. The inlets and outlets for the exhaust gas are arranged relatively close to the inlets and outlets for the cooling media, so that the flow directions of the exhaust gas and the cooling media intersect in this region.
Such tubular heat exchangers were later abandoned as exhaust gas heat exchangers because they were unsatisfactory in performance and too cumbersome. The bulkiness of the heat exchangers arose, in part, because of the required external housing (mostly in cylindrical shape), which encloses the bundle and borders the flow channels for the coolant on the outside. As a rule, exhaust gas heat exchangers must be very space-saving while simultaneously providing high performance parameters, in particular, for vehicular applications. Round cross-sectional shapes have a lower degree of space utilization, and are thus undesirable.
For these reason, and for cost reasons as well, the switch was made to so-called housingless plate heat exchangers, as shown, for example, in German Utility Patent No. 296 16 354 (which originates from the applicant).
Still another prior art plate-type heat exchanger is shown in European Patent At Application No. 677 715. This plate-type heat exchanger may be adventageously used because the exhaust gas can flow through the heat exchanger without significant diversions that cause pressure losses. However, for a case in which the exhaust gas is cooled with water, the stack of heat exchanger plates is still enclosed by a housing, which leads to the already mentioned shortcomings. The flexibility of the heat exchanger with respect to different connection positions, especially for the coolant connections, is also in need of improvement. The plate stack is designed according to the so-called bar-plate design, so that many individual components are present that must be joined. This can be viewed as costly.
It is therefore an object of the invention to provide a compact, efficient heat exchanger.
It is a further object of the invention to provide a heat exchanger that can be manufactured cost effectively.
It is a still further object of the invention to provide a heat exchanger that exhibits better flexibility with respect to incorporation into space and connection limitations.